1. Field of the Invention
The invention relates to the field of recycling film waste that contains an adhesive.
2. Discussion of the Prior Art
German Patent Application DE 195 31 886 A1 teaches a continuous process for reclaiming raw materials from coated films. In this process, the coatings are removed from magnetic tapes or also photographic films, so that the materials in the tapes or films can be reclaimed and also, so that the carrier material that is now free of the coating can be processed. This prior art reference does not address the problems that exist in dealing with film waste that is coated with an adhesive.
German Patent DE 21 14 304 B2 discloses a process for reclaiming polymers from waste products, whereby the waste products are continuously reduced in size and rendered to a fleece, which is then chopped or beaten into small packets of fiber. A disc compactor may be used for subsequently compacting the fiber packets. The waste products occur in the manufacture of synthetic fibers. This patent also does not discuss treating film waste that is coated with adhesive.
The closest prior art for dealing with adhesive-coated film waste is German Patent DE 42 21 681 C2, which describes a method of treating, for example, plastic waste from a stamping process, the waste frequently designated as “stamp skeletons.” The process may also be used to treat waste that includes adhesive tapes, large-area adhesive films, etc.
The stickiness or adhesive strength of the adhesive is a problem, because the adhesive sticks to the equipment that is used for reducing the size of the material and gums it up. Also, higher maintenance may be required to keep the equipment in operating condition.
The prior art teaches adding adhesive-free material to the adhesive-coated material, i.e., the film waste, in order to reduce the adhesive strength of the total volume of the waste to be processed. This requires a comparatively complex logistic, because the non-adhesive containing material that is to be added to the adhesive-coated film waste should preferably be from the same group of material as that of the film waste. For example, when processing adhesive-coated polyethylene (PE) film, additives of non-adhesive PE material are preferably used. This ensures that the material that is reclaimed is as pure as possible. This is important, because, otherwise, the properties of products made from the reclaimed material would suffer significant deterioration.
Aside from the complication of managing the process or preparing for implementing the process, is the disadvantage that the adhesive strength of the adhesive-coated film waste remains unchanged. Adding non-adhesive waste only increases the likelihood that the sticky surfaces of the adhesive-coated film waste, as long as they haven't clumped together, will be covered by the non-adhesive waste, thereby reducing the total surface area of sticky material. The problem is that the adhesive strength of the sticky surfaces remains undiminished and when the sticky surfaces of this mixed waste come into contact with the processing equipment, the danger of gumming up the processing equipment remains unchanged, albeit in a reduced frequency.
Despite these limitations, processing adhesive-coated film waste is fundamentally desirable, because the only alternative now is a thermal treatment of film waste in order to remove it from the stream of waste material. It is desirable for ecological reasons to recycle film material that is made from petroleum products, i.e., not from renewable resources, and to feed the recycled material back into the stream of usable material. It is also important that the process of reclaiming material be cost-effective, so that the re-use of the film waste is encouraged out of economic considerations.